Popular smoking articles, such as cigarettes, have a substantially cylindrical rod-shaped structure and include a charge, roll or column of smokable material, such as shredded tobacco (e.g., in cut filler form), surrounded by a paper wrapper, thereby forming a so-called “smokable rod,” “tobacco rod” or “cigarette rod.” Normally, a cigarette has a cylindrical filter element aligned in an end-to-end relationship with the tobacco rod. Preferably, a filter element comprises plasticized cellulose acetate tow circumscribed by a paper material known as “plug wrap.” Certain filter elements can incorporate polyhydric alcohols. See, for example, UK Pat. Spec. 755,475. Certain cigarettes incorporate a filter element having multiple segments, and one of those segments can comprise activated charcoal particles. See, for example, U.S. Pat. Nos. 5,360,023 to Blakley et al. and 6,537,186 to Veluz. Preferably, the filter element is attached to one end of the tobacco rod using a circumscribing wrapping material known as “tipping paper.” It also has become desirable to perforate the tipping material and plug wrap, in order to provide dilution of drawn mainstream smoke with ambient air. Descriptions of cigarettes and the various components thereof are set forth in Tobacco Production, Chemistry and Technology, Davis et al. (Eds.) (1999). A cigarette is employed by a smoker by lighting one end thereof and burning the tobacco rod. The smoker then receives mainstream smoke into his/her mouth by drawing on the opposite end (e.g., the filter end) of the cigarette.
Through the years, there have been proposed various methods for altering the composition of mainstream tobacco smoke. In PCT Application Pub. No. WO 02/37990 to Bereman, it has been suggested that metallic particles and/or carbonaceous particles can be incorporated into the smokable material of a cigarette in an attempt to reduce the amounts of certain compounds in the smoke produced by that cigarette. In U.S. Patent Application Pub. No. 2005/0066986 to Nestor et al., it has been suggested that a tobacco rod can incorporate tobacco filler combined with an aerosol-forming material, such as glycerin. U.S. Pat. No. 6,874,508 to Shafer et al. proposes a cigarette having a paper wrapped tobacco rod having a tip portion that is treated with an additive, such as potassium bicarbonate, sodium chloride or potassium phosphate.
Various tobacco substitute materials have been proposed, and substantial listings of examples of such materials can be found in U.S. Pat. Nos. 4,079,742 to Rainer et al. and 4,771,795 to White et al. References describing tobacco substitutes are also set forth in the background section of U.S. Patent Application Pub. No. 2007/0215168 to Banerjee et al.
Numerous references have proposed various smoking articles of altered format and configuration, or of a type that generate flavored vapor, visible aerosol, or a mixture of flavored vapor and visible aerosol. See, for example, those references set forth in the background section of US 2007/0215168 to Banerjee et al. Furthermore, certain types of such smoking articles have been commercially marketed under the brand names “Premier” and “Eclipse” by R. J. Reynolds Tobacco Company, and under the brand name “Accord” by Philip Morris Inc. More recently, it has been suggested that the carbonaceous fuel elements of those types of cigarettes can incorporate ultrafine particles of metals and metal oxides. See, for example, US Pat. Application Pub. No. 2005/0274390 to Banerjee et al., which is incorporated by reference herein.
Smoking articles that employ tobacco substitute materials and smoking articles that employ sources of heat other than tobacco cut filler to produce tobacco-flavored vapors or tobacco-flavored visible aerosols have not received widespread commercial success. However, it would be highly desirable to provide a smoking article that demonstrates the ability to provide to a smoker many of the benefits and advantages of conventional cigarette smoking, while reducing delivery of incomplete combustion and pyrolysis products.